When quinoline (Formula (1)) is nitrated, ##STR1##
a mixture of nitroquinoline position isomers is formed, which includes 5-nitroquinoline, 8-nitroquinoline and relatively small amounts of other nitroquinoline compounds.
5-nitroquinoline (Formula (2)) is a useful intermediate ##STR2##
for certain organic syntheses. Among other utilities, 5-nitroquinoline can be used as an intermediate in the synthesis of 10,11-cyclopropyldibenzosuberane derivatives as described in PCT Patent Application No. PCT/US94/04215 (Publication Number WO 94/24107).
8-Nitroquinoline (Formula (3)) is also a useful intermediate for certain organic syntheses. ##STR3##
Among other utilities, 8-nitroquinoline can be used in the synthesis of 8-aminoquinoline, which can be used in a number of syntheses of organic products, see e.g. EP 388619 (synthesis of pyridine-2,3-dicarboxylic acid), Merck Index, Tenth Edition, Merck & Co., 1983, pg. 707 (synthesis of 8-hydroxyquinoline) and Merck, pg. 1037 (synthesis of 1,10-phenanthroline).
The mixture of products obtained during the nitration of quinoline was disclosed in a report published in 1885 by Claus and Kramer in Chem. Ber., (1885), 18, 1243. Seven years later, S. F. Dufton in J. Chem. Soc., (1892), 61, 783, reported that by dissolving the mixture of nitro products in a large quantity of very dilute nitric acid and cooling, the 5-nitroquinoline isomer selectively separated as the nitrate salt. Later work by W. Meigan (J. Prakt. Chem., (1908), 77, 472); R. P. Dickshoorn (Rec. Trav. Chim., (1929), 48, 147); L. F. Fieser and E. B. Herschberg (J. Am. Chem. Soc., (1940), 62, 1640); and V. M. Dziomko and I. A. Krasavin (Khim Geterotsikl. Soedin., Sb. 1, Azotsoderzhashchie Geterosikly, 1967, 281; C.A., 1969, 70, 77748c), utilized this technique to prepare and separate quantities of 5-nitroquinoline and 8-nitroquinoline.
It must be noted that the use of a large volume of dilute acid is typically undesirable in any chemical process because of waste disposal issues.
What is needed are processes to selectively separate 5-nitroquinoline and 8-nitroquinoline from a mixture of nitroquinoline position isomers that provides a good separation of each isomer in relatively pure form, without the use of a large volume of dilute acid.